switchreal.f90

基于linux操作下的fortran快速付立变换的程序

 	subroutine switchreal(includelast,n1dfft,n2,n2eff,lot,n1zt,lzt,zt,zw)
	implicit real*8 (a-h,o-z)
	dimension zw(2,lot,n2),zt(2,lzt,n1zt)

        if(includelast==1)then

!        Compute symmetric and antisymmetric combinations
         do j=1,n1dfft
          zw(1,j,1)=zt(1,1,2*j-1)
          zw(2,j,1)=zt(1,1,2*j  )
         enddo
         do i=2,n2eff
          do j=1,n1dfft
           zw(1,j,i)=      zt(1,i,2*j-1)-zt(2,i,2*j)
           zw(2,j,i)=      zt(2,i,2*j-1)+zt(1,i,2*j)
           zw(1,j,n2+2-i)= zt(1,i,2*j-1)+zt(2,i,2*j)
           zw(2,j,n2+2-i)=-zt(2,i,2*j-1)+zt(1,i,2*j)
          enddo
         enddo

        else 

!        An odd number of FFTs

!        Compute symmetric and antisymmetric combinations
         do j=1,n1dfft-1
          zw(1,j,1)=zt(1,1,2*j-1)
          zw(2,j,1)=zt(1,1,2*j  )
         enddo
         zw(1,n1dfft,1)=zt(1,1,2*n1dfft-1)
         zw(2,n1dfft,1)=0.0d0
         do i=2,n2eff
          do j=1,n1dfft-1
           zw(1,j,i)=      zt(1,i,2*j-1)-zt(2,i,2*j)
           zw(2,j,i)=      zt(2,i,2*j-1)+zt(1,i,2*j)
           zw(1,j,n2+2-i)= zt(1,i,2*j-1)+zt(2,i,2*j)
           zw(2,j,n2+2-i)=-zt(2,i,2*j-1)+zt(1,i,2*j)
          enddo
          zw(1,n1dfft,i)=      zt(1,i,2*n1dfft-1)
          zw(2,n1dfft,i)=      zt(2,i,2*n1dfft-1)
          zw(1,n1dfft,n2+2-i)= zt(1,i,2*n1dfft-1)
          zw(2,n1dfft,n2+2-i)=-zt(2,i,2*n1dfft-1)
         enddo

        endif

        end